Rotary liquid pump



April 1943- w. w. DAVIDSON 2,316,318

ROTARY LIQUID PUMP Filed July 8, 1959 5 Sheets-Sheet 1 April 1943- w. w.DAVIDSON 2,316,318

ROTARY LIQUID PUMP Filed July 8, 1939 5 Sheets-Sheet 2 l v 7 J7 v 92/ 2]J0 I I E April 13, 1943. w. w. DAVIDSON ROTARY LIQUID PUMP sSheets-Sheet 4 NN N fiuznaon- Waxzdiavwazz W W Filed July 8, 1959Patented Apr. 13, 1943 UNITED-STATES PATENT OFFICE ROTARY LIQUID PUMPWilliam Ward Davidson, Evanston, Ill.

Application July 8, 1939, Serial No. 283,480 1: Claims. (Cl. 103-121)The present invention relates generally to rotary pumps, and moreparticularly to a new and improved rotary pump of the rotary cylindertype designed to handle a large volume of liquid at full motor speed.

I provide a liquid pump which will operate at full motor speed, so thatthe motor shaft may be connected directly to the pump shaft. Thiseliminates all reduction gearing, belts and pulleys, and all bearing andseal wear which takes place in conventional pumps where belt tension ishigh to prevent slippage. In the present invention wear upon the sealsis further minimized by subjecting them to the intake pressure insteadof the head pressure developed by the pump.

Not only this, but for a given volume the pump of the invention is madesmaller than those designed for slower speeds, the construction beingsuch that perfect balance and elimination of vibration are attained bythe structural features employed, including running both the rotor andthe cylinder on their own true centers.

Moreover, with side thrusts removed from the bearings, improved bearingarrangements are employed where both the cylinder and the rotor arerotatably supported at spaced points, each being a single integral unitwhose rotational balance is established permanently inthe machiningoperation, with three of the four bearings employed in the inventionformed at one time in one of the two members making up the sealedcasing.

In providing my improved pump care has also been given to the removal ofend thrusts that cause wear. The intake and exhaust are arranged toaccomplish this, and the end walls of the pump compartment are rigidrelative to each other so as to eliminate any possible give between themwhich would allow the end walls to be spread apart by compressionpressures, and thereby induce heavy end thrusts.

Furthermore, one of the chief purposes of the present invention is toprovide a pump of rug ed simplicity having a minimum of parts andadjustments, and one which is strong enough to withstand the heaviest ofwork loads that can be imposed upon it by the weight andincompressibility of liquids. In this connection one of the embodimentsis a comparatively constant flow pump with the pulsations sufficientlyeven that an expansion chamber can be eliminated.

Another object of the invention is to provide a pump which is easily andinexpensively manufactured from simple castings and parts made andfinished without necessitating the use of other than elementarymachine-shop practice.

These being among the objects of the invention, other and furtherobjects, including those related to ease of assembly and adjustment, andaccessibility to all parts for repairs and replacement, will becomeapparent from the drawings, the description relating thereto, and theappended claims.

Referring now to the drawings:

Fig. 1 is a sectional view of a preferred form of the invention, takenupon a longitudinal plane through the center of the pump;

Fig. 2 is a transverse section taken upon line 2-2 of Fig. 1;

Figs. 3 and 4 are fragmentary transverse sections similar to Fig. 2,showing the piston, cylinder and vane construction of the pump invarious operating positions;

Fig. 5 is a perspective view showing the structural details of therotatable cylindrical member of the pump as an article of manufacture;

Fig. 6 is a perspective view of the rotatable piston as an article ofmanufacture;

Fig. 7 is a sectional view of another form of the invention, taken upona longitudinal plane through the center of the pump;

Fig. 8 is a transverse section taken upon line 8-8 of Fig. "I; and

Fig. 9 is a perspective view partly in section, showing a portion of therotatable piston of Fig.7 as assembled.

The general organization of the pump illustrated comprises an innercylindrical member or piston I0, and an outer cylindrical member orcylinder I I, eccentrically mounted to rotate about their own truecenters, with an outer cylindrical surface I3 upon the piston Ilidisposed tangential to an inner cylindrical surface I2 upon the cylinderII to provide a crescent-shaped pump chamber I8 between them which isdivided into pumping compartments by a vane ll rigidly carried by thepiston I0.

The cylinder is journaled in a casing I1 upon axially spaced bearings 23and 24, machinedon the inner walls of the vcasing, and the pistonextends beyond both ends of the cylinder II. At its large end 2| thepiston is journaled in: and terminates within thecasing I'I, while atits smaller end 20 the piston is journaled in the cover member I8. Theends of the pump chamber I9 are sealed by two stationary shoulders I5and I6, machined upon. the casing I1 and cover member I8, respectively.The piston III is directly driven by a prime mover (not shown) throughthe end 20, and the cylinder II is driven from the piston l8 through thevane l4.

Referring now to the structural characteristics of the pump in furtherdetail attention is directed to the casing H, which is made of castmetal and provided with a flanged base 22 for supporting the pump as aunit. The main part of the casing is cast hollow, with a reduced portion21 at one end and an enlarged portion 29 at the other end having a boss23 thereon.

The two axially spaced bearings 23 and 24 are machined in the enlargedportion 23 in a way providing an enlarged compartment 23 between them,which serves as an exhaust compartment into which liquid under pressureis forced by the pumping elements. From the compartment 25 the liquidunder pressure passes out through a threaded opening in the boss 23 intoa conduit (not shown) threaded therein.

In the reduced portion 21 of the casing l1 a bearing 28 of lesserdiameter is machined eccentric to the bearings 23 and 24. These bearings2-3 and 24 support the cylinder II as already described, while thebearing 28 supports the end 2| of the piston. This arrangement ofbearings has several advantages, where, as in this case, the pump hasfour bearings. Three of the four bearings are those Just described, viz:23, 24 and 28. These three bearings are located in the casing l1, andare machined all at the same time when the casing is being finished.They therefore automatically line up identically for all pumps and foreach casing in their proper relation. Only one of the four bearings isin the cover member I8, and this one is concentric to one of the three.Thus the task of drilling the cover member and marking it for correctalinement is comparatively simple-only one bearin need be accounted forin the second member instead of two or more, as is the usual situation.

Beyond the end of the piston the end portion 21 is cast with an enlargedportion, as at 33, for a short distance to provide head room forlongitudinal movement of the piston, so that the piston may be movedaxially in the bearing 23 to take up excess clearances between movingparts, as will be more fully described later.

Beyond the enlarged portion 30 the reduced end 21 is threaded, as at 3|,to receive a liquid intake conduit (not shown), and at its enlarged end28 the casing I1 is faced to mate with the end cover l3 in partialtelescoping relationship limited by a sealing shim 32, of predeterminedthickness, disposed between facing shoulders upon the respectivemembers.

The end cover I8 comprises a metal casting having an elongated centralportion 33 drilled out, as at 34, to provide a bearing surface ofsubstantial length which Journals the reduced end 28 of the piston overa major portion of its length. Near the outer end the rest of theelonated portion 33 has an expanded region forming a seal chamber 38 inwhich are suitably mounted two spaced sealing units 38 and 31, that areheld apart by a compression spring 38.

Two members of the sealing units comprise oppositely facing rings 4|that rotate with the shaft and are mounted in sealed-engagementtherewith upon resilient washers 42 subjected directly to the pressureof the spring 33. Stationary rings 43, supported in sealed relation tothe cover l8 by means of resilient washers 44, provide the other membersof the units. In this way the sealed relationship between the relativemoving rings 4| and 43 is maintained in direct relation to the tensionof the spring 38, a tension which may be increased or lessened by springreplacement, depending upon working pressures to which the seals aresubjected. Moreover, the sealing elements are where they are readilyaccessible for repair and replacement at all times, it being onlynecessary to remove the cap 48 which holds them in place.

As more particularly shown in Fig. 6, the enlarged end portion 2| of thepiston I0 is hollow, being preferably provided with a cylindrical wallof uniform thickness and a squared shoulder 45 between the enlargedportion and the reduced shaft portion 20.

A longitudinal slot 46, of predetermined width, is cut through the wallfrom the shoulder 45 to a point 41 spaced from the shoulder a distanceapproximately substantially equal to the distance between the shouldersl5 and IS in the casing 11. The outer corners of the slot 48 are roundedconcavely to provide portions 5| of a cylindrical surface along eachside. With regard to the direction the piston rotates, the trailing side53 is cut away, as at 52, to provide intake ports opening through thewall.

The outer cylindrical surface of the enlarged portion 2|. including theportion journaled in the bearing 28, is of uniform diameter throughout.In this way the piston is adapted for use with cylinders of different orvarying widths. If in time the shoulders I5 and I8 wear, the shim 32 maybe replaced with a thinner one to take up on the wear without giving thepiston any attention, the end 2| of the piston l0 merely telescoping alittle further into the reduced portion 21 of the casing 11. Adjacentthe shoulder 45 the enlarged end portion 2| is drilled and threaded, asat 53. along an axis chordal thereto to receive a locking screw 54 (Fig.l) to lock the vane l4 in place.

In cooperation with the function of the seals 38 and 31 and the bearingdescribed, I provide a drilled-out passageway 38 through the reduced end20 of the piston leading from the enlarged space 38 between the sealingelements 38 and 31 to the hollow enlarged end portion 21 of the pistonII. This connects the seals to the intake pressure of the liquid. Anyliquid under head pressure escaping other than through the exhaustporthas only two ways to go, one way along the bearing 28 where itenters the column of liquid moving into the hollow portion of the pistonI 3 to reach ultimately the exhaust port 28, while the other directionfor the liquid under pressure to escape is along the shoulder I3 throughthe bearing 34. This path of escape is obstructed by the seal 38, butany liquid leaking past the seal reaches the compartment '35 from whichit is returned through the passageway 39 also to the liquid entering thepump chamber.

Movement of some liquid along the bearings is desirable because it actsas a lubricant for the bearing surfaces. In the present invention thisis made possible without fear of leakage, and in this connection it willbe appreciated that the inner bearing seal 38 merely operates to controlthe volumetric efllciency of the pump by preventing too much liquidescaping.

In some installations the inner seal 38 may be dispensed with where theback pressure factor upon the pump is low. On the other hand, the seal31 prevents liquid at pump intake pressure from escaping into theatmosphere, if the pressure is higher than atmospheric pressure, and,contra, in event the intake pressure is sub-atmospheric the seal 31prevents air from bleeding into the pump. In this way the purity of theliquid being pumped is maintained, the bearings lubricated, volumetricefliciency maintained, and leakage prevented.

Referring now to the structure of the vane ll, the same is pattern cutfrom a piece of flat stock of uniform thickness to a shape (best shownin Fig. 1) in which a substantially rectangular portion 55 is providedwith an axial length the same as the length of the cylinder IS. Theportion 55 is also dimensioned to extend radially a distancesubstantially less than the distance between the inner surface of theenlarged portion 2| of the piston and the bearings 23 and 24. At itsright end (as viewed in Fig. 1) the vane is cut away, as at 51, adistance greater than the thickness of the end wall 58; while at theleft end the vane extends beyond the end of the portion 55, as at 60,and subtends the ends of the wall 48 of the piston, from which point itis cut away substantially on an angle, as at iii. The bottom side of thevane may abut the side of the wall opposite the slot 46, as at 62 in away bisecting the hollow portion of the piston l0.

Longitudinally near the center the vane is drilled out to provideopenings 63, primarily designed to permit liquid in the hollow portion2| of the piston to move freely from one side of the vane to the otherin reaching the inlet ports 52, although the openings are so located asto provide a weight-balancing influence also.

With the vane bisecting the hollow compartment and rotatable with thepiston, it is possible to handle more liquid effectively than would bepossible otherwise. The size of the intake port through the piston tionto the size of the tubing to which the inlet 3| is connected, and fullspeed of movement of the liquid past the vane is enhanced by centrifugalforces induced by the vane.

When the liquid moves within thesweep of the vane it is immediatelyimpelled to rotate at high speed. At this high speed the liquid has aninherent centrifugal pressure which assists in moving it intermittentlyfrom a radially static position into the pump chamber through the inletports upon the intake cycle of the pump members. This centrifugal actionalso assists in drawing the liquid into the pump casing, relieving thepump chamber of apossible vacuum load normally present with conventionalarrangements.

The particular structureof the vane is such that in assembly the end BI!is inserted through the slot 46 first, and'pushed rearwardly with thebottom side 62 coming into contact with the far side of the hollowportion of the piston. The vane is then pushed to the left until theright edge is flush with the shoulder 45. The locking screw 54 is theninserted and tightened to hold the vane in place. Dowels 164 are theninserted through the wall into the edge 52 of the vane, to hold the samerigidly in place.

Mounted for rotation in the bearings 23 and 24 is the cylinder I I,having a sliding and sealed relationship with the vane. The cylindricalmember II is substantially spool-shaped, having a reduced intermediateportion or channel BI and two rims 65, which are. connected by anintermediate portion 66 running axially between them and across thereduced portion 64, with an opening 68 through the reduced portion 5| toone side of the portion 66, forming the exhaust port. The rims 65 aremachined to rotate in the bearings 23 and 24, and the reduced portion 64cooperates is determined upon its relawith the enlarged portion 25 ofthe casing II to provide an exhaust chamber for the pump.

The interconnecting portion 56 provides suflicient metal mass for alongitudinal groove 61 to be cut upon the inner cylindrical pump surfacel2 of the cylinder II, in a way affording suflicient head room for theend of the vane to move back and forth when canted relative to thecylinder, as the cylinder and the piston rotate eccentrically. The walls10 of the groove 61 are arcuately cut away throughout their length todefine sections of a surface of revolution identical with that of thecut-away portions 5! upon the piston Ill.

Rocker segments H are provided to fit in the groove 51 between thearcuate walls Ill of the cylinder and the sides of the portion 56 of thevane ll. Thus as the elements rotate the flat faces 12 have slidingrelationship with the sides of the extension 56 on the vane l4, and arocking relation with the walls ID on the cylinder, in a way sealing thepump compartments upon opposite sides of the vane. The face 12 of thesegments ll located upon the intake side of the vane is grooved (notshown) to liberate the groove 51 of pressure factors developed by theaction of the vane between the segments 1 I.

In the construction described, it will be noted that as the piston andthe cylinder reach a point of tangency at the vane the rocker segment'll mate with the cylindrical surfaces 5| upon the piston. Thisarrangement has the advantage of a high volumetric efficiency which-isnot present where the segments H are disposed deep within the channel61. If the segments were to be disposed deep within the channel 51 therewould be a portion of the channel next to the cylinder lust as wide asthe channel beyond the segments, to allow for the relative cantingmovement of the vane. This space is dead space, and although of lessersignificance where an incompressible liquid is being pumped thisparticular construction has a broader application in use with fluidpumps where complete displacement of a compressible substance is highlyimportant to the pumps emciency.

In addition, this arrangement of parts permits a greater compactness ofconstruction, since the bearing areas between the vane and the segments1| are never as little as half the area of th flat sides of thesegments. This is important because where, as in the particularconstruction disclosed, the drive between the two rotating pump membersis carried by the vane; the segments would be displaced or cause abinding between the segments and the vane if the area contact was halfor less than half.

This development of a compact construction, as shown, brings about otheradvantages regarding vibration control. A lesser radius of overallweight distribution is entailed, and this permits a wider range in theapportionment of mass needed to balance centrifugal inertias. In theparticular embodiment illustrated it will be noted that all rotatingunits of mass ar dynamically balanced. The vane ll, in addition toextending beyond the outer cylindrical surface, extends in ,adiametrically opposite direction toward the other side of the center ofrotation with substantial portions of its mass drilled away on the sideof the center of rotation next to the extended portion. Thus thedrilled-out portions serve, as mentioned, a double purpose in permittingfree movement of liquid inside the hollow cylinder from one side of thevane to the other, and proportions the metal to allow for the amount ofmetal which is removed from the piston portion to provide the intakeports. Since all surfaces of the piston and vane are machined, and noallowances have to be made for casting variations, it is readilyapparent that the vane and piston are standardized parts that do notvary, particularly as regards rotational weight distribution.

Referring again to the cylinder on this point, all portions are machinedexcept the reduced central portion 84, and since this entails a malecoring-an operation which is easily controlled as to metaldistributionlt is readily apparent that the cylindrical member can bestandardized to slight variance. The stock lost in providing the exhaustports is balanced by the inner connecting portion 88, which can bevaried in mass by the width of the channel 81, it being appreciated thatthe mass provided by the portion 66 does not extend the full length ofthe cylinder as does the groove 81, thus making up for a seeming excesswhich might appear to be present in viewing the cylinder crosssectionally, as shown in Figs. 2, 3 and 4.

Having pointed out the structural characteristics which, to those.skilled in the art, show that the parts making up the present pump canbe produced and machined within elementary shop practice, it is to benoted that assemblage of the parts is also very easily had. These twofactors reduce the expense materially of the invention as compared withpumps having comparable pumping capacities.

In assembling the pump the casing I! is upended with the large endupward. The cylinder H is lowered into place with the exhaust port 68 onthe side of the axial portion 66 next to the boss 28.

The piston and vane assembly is inserted into the casing H, with thevane disposed in the slot The segment H upon the side of the vane nextto the intake ports is next inserted in place, a position it willreadily assume since the vane has plenty of room into which to move toaccommodate it. After the first segment II is in place, as described,the second one is tapped into place very easily, since it has a smoothcontinuous surface the full path of its travel, even when tansencybetween the pump members happens to occur at the vane.

With the pump elements asembled in place the cover portion IS, withoutthe gasket 32, is telescoped over the reduced portion 20 of the pistonuntil it comes to rest solidly against the ends of the cylinder, thehollow end 21 of the piston permitting this to'take place by telescopingfurther into the hearing at 28. Preferably pressure is appliedlongitudinally to collapse all clearances present with the assembledparts, and the space where the gasket 32 is to be received is measuredeither before or after, preferably after, the pump members have beenrotated a few times to seat them. The cover member is then removed andthe gasket 32, of a slightly greater thickness, is located in place andthe cover plate returned and fastened in place by suitable means, suchas bolts not shown)-dowels being used to locate the cover and casing incorrect relationship. Thereafter the sealing members are assembled inplace in their positions, as already described, with the cap 40 finallyassembled to hold the sealing members in place.

Referring now to Figs. 7, 8 and 8 an embodiment of the invention isshown wherein the pump is constructed and arranged to have two pumpingchambers A and B. In this embodiment I provide a pump construction whichnot only has substantially all the advantages and structuralcharacteristics of the embodiment Just described but also has the addedadvantage of providing a substantially steady output. With thisparticular embodiment an expansion air dome upon the exhaust line is notneeded since the exhaust is substantially free from pulsation. Althoughit is possible to make the main casing of a single casting similar tothe casing ll shown in Fig. 1, I prefer, in this instance, for the sakeof convenience in performing the necessary machining operations, to castthe casing in two parts, a cylindrical member and an end portion 8|, andsecure them together with bolts 82. The cylindrical member 80 isprovided with four axially spaced bearings ll, 84, and 86 machined uponthe inner surface thereof with compartments 81 and 88 cast in the wallsthereof between the bearings 83 and 84 and between bearings 85 and 88,respectively. The compartments 81 and 88 serve as exhaust compartmentsin a manner similar to that shown in Fig. 1. From both compartments theliquid under pressure is exhausted through the common opening 90 castand threaded in the boss 9|.

The provision of the compartments 8'! and 88 as shown not only serve asexhaust passageways but also as relief portions in the casting whichreduces the amount of metal that has to be machined in order to providethe bearing surfaces required. In this connection a groove 92 isprovided in the casting upon the inner surface thereof between bearings84 and 85 for the same purpose.

The following description will be confined to the rotating cylinders 93and 94, the vanes 95 and 96 and that portion of the piston 9'! locatedwithin the confines of the cylinder 80. The construction of the pump inFig. '7 is otherwise substantially unchanged from that shown in Fig. 1.Consequently, like numbers will be employed to identify like parts whichhave already been described.

The two cylinders 93 and 94 are substantially identical, being designedthis way to accomplish manufacturing economies. However, they have beenidentified in the drawings by separate numerals to relate them to theleft hand and the right hand pump compartments, respectively, as viewedin Fig. 7. These members are rotatably journaled in the bearings 83 and84 and the bearings 85 and 86, respectively. The cylinders 93 and 94 arenot as long as cylinder H but otherwise have substantially the samestructural characteristics as the cylinder H. Related parts of thecylinder II and the cylinders 93 and 94 are identified with the suflix aand the description already supplied concerning cylinder II applies herealso.

As more particularly shown in Fig. 9, the piston 91 is hollow. Radially,at any given point along the axis the walls are of uniform thickness andat the end adjacent the shoulder 45a are of greater thickness to providemore stock to hold the vane 96 in place.

Over that portion of the piston within the boundaries of the cylinder 93the wall of the piston is provided with a slot I00 and on its trailingside, the slot is further cut away as at IOI to provide an intakeopening through the wall from the interior of the piston. In thisinstance, however, the outer corners of the slot I00 are not roundedconcavely as in the first embodiment described and the rocker segmentsIla are cut away to clear the piston.

The vane 95 in the slot I is rectangular and slips radially into theslot from the outside where it comes to rest with its lower end I02resting against the far side of the wall of the piston where it isdoweled in place by dowels I03. This vane is thereby well supported tocarry the load of positively driving the cylinder from the piston.

Against the right end of the vane a spacing ring I04 is telescoped overthe piston and held in place against the right end of the vane 95 bydowels I05, the ring being further held in place upon the piston by setscrews I01 locked in place by followers I00. The ring assembly operatesto hold placement.

Over the remaining portion of the piston adjacent to the reduced end 20a longitudinal groove H0 of square sides and square corners is cut intothe wall of the piston without being cut all the way through the wal Thegroove IIO is angularly displaced through l80 with respect to the slotI00 and receives the vane 96 therein in supported relationship by a setscrew a and end dowels III also driven through the ring I00. The inletopening for the second pump compartment is a slot! I2 cut through thethickened part of the shaft or piston upon the trailing side of the vane96.

It will be observed that this construction provides inherently adynamically balanced pump. The rotating members rotate on their own trueaxes and each of the assemblies is dynamically balanced. In the piston,the vanes where they intersect the piston merely replace the metal cutaway to receive each of them, and where they extend beyond the outersurface they extend equal distances in opposite directions, one

\ vane balancing the other. Inside the piston the vane 95 is dynamicallybalanced and the inlet openings are diametrically opposed. The ring I04is also dynamically balanced within its own weight, Consequently theopening H3 in the vane 95 that is provided to permit free passage ofliquid from one side of the vane to the other may be of any size desiredprovided the center thereof intersects the axis of the piston. In thecylinders it inders 93 and 04 are displaced 180 with respect to eachother so that any individual unbalance.

in one is counteracted by the same unbalance in the other. Need forspecial correction for balance is therebyeliminated.

In assembling the pump shown in Fig. 'I the piston with the vanes andring in place is inserted inside the cylinder 80 approximately to thatpoint which it will assume when the assembly is completed. One of thecylinders is then located in place with the segments Ila insertedthereafter and the cover for that end of the cylinder 80 is bolted intoplace with the piston received in the respective bearing. The cylinder80 is then upended to receive the other cylinder in place, after whichthe other cover is bolted down solid.

The procedure thereafter is substantially the same as with the firstdescribed embodiment wherein the piston is turned a couple of turns totake up all clearances between the assembled parts and the measurementis made for the insertionof the appropriate shim 32 which will determinethe clearance in the moving parts desired.

Thus having described the illustrated embodithe vane Siagflinst radial(#:V

' many 'of the parts serving dual ments of the invention, it will beseen a novel and improved liquid pump has been provided whicheliminates, for all practical purposes, leakage and vibrationencountered in pumps of conventional construction. Moreover, the partsare simple in construction, inexpensive to manufacture, assemble andmaintain in operation, with functions not heretofore accomplished in theart. Consequently, of the inve' tion has been illustrated and described;it will be apparent to those skilled in the art that variousmodifications and changes may be made therein without departing from thespirit of the invention, the scope of which is commensurate with theappended claims.

I claim as my invention:

1. For use in a rotary pump of the type de scribed, a hollow cylindricalpiston open at one end and having a longitudinal slot having differentwidths and extending through the side will be noted that the identicalcylwall intermediate the ends, a longitudinal vane extending from theinternal surface of the piston diametrically opposite the slot outwardlythrough the slot, the thickness of the vane being substantially lessthan the greatest width of the slot, and means diametrically oppositethe slot and rigid with the piston engaging an edge of the vane forretaining the vane and piston in fixed relation, the vane having atransverse opening within the piston.

2. In a rotary pump of the type described, a

rotatable cylinder, a hollow piston rotatably mounted eccentric to thecylinder and tangential to the inner surface thereof definingtherewith apump chamber, the piston having a slot extending through a wallintermediate the ends of the piston, a longitudinal vane extendingoutwardly through the slot from the internal surface of the pistondiametrically opposite the slot into sliding engagement with thecylinder dividing the pump chamber into intake and discharge sectionseach having a port therein, and dowels rigid with the piston engagingthe vane within the piston and retaining the vane in rigid relation tothe piston. a

3. In a rotary pump of the type described. a rotatable cylinder, ahollow piston rotatably mounted eccentric to the cylinder and tangentialto the inner surface thereof defining a pump chamber, the piston havinga slot extending through its side wall intermediate the ends of saidpiston and parallel to the axis of the piston,

a casing supporting the piston and cylinder and having inlet and outletports communicating with the pump chamber, a longitudinal vane extendingdiametrically outwardly through the slot from the internal surface ofthe piston diametrically opposite the slot into sliding engagement withthe cylinder, dividing the pump chamber into intake and dischargesections, each of said sections having a port therein, and meansextending through a wall of the piston intermediate the ends of saidpiston engaging the vane for maintaining the vane in rigid relation tothe piston.

4. In a rotary pump of the type described, a rotatable cylinder, ahollow piston rotatably mounted eccentric to the cylinder and tangentialto the inner surface thereof defining therewith a pump chamber, alongitudinal vane extending outwardly-through a longitudinal slot in thepiston from the inner surface of the piston diametrically opposite theslot into sliding engagement with the cylinder dividing the pump chamberalthough a single preferred embodiment into intake and dischargesections, each of said sections having a port therein, and means rigidwith the piston engaging the vane within the piston for retaining thevane and piston in rigid relation.

5. For use in a rotary pump of the type described, a hollow cylindricalpiston open at one end only and having a longitudinal slot extendingthrough the side wall intermediate the ends, a solid planar vaneextending from within the piston diametrically outwardly through theslot, and means diametrically opposite the slot and rigid with thepiston engaging the inner end of the vane for retaining the vane andpiston in fixed relation, the vane extending inwardly into the pistonand having a cross sectional area smaller than the area of the slot todefine a piston port.

6. In a rotary pump, a casing having a conduit opening and parallel endwalls, at least one of the end walls being removable, cylinder bearingsin the casing intermediate the end walls, piston hearings in the endwalls, an inlet in an end wall, the axis of the piston bearings beingspaced from and parallel to the axis of the cylinder bearings, a hollowcylindrical piston journalled in the piston bearings, one end of thepiston being reduced in diameter to form a shoulder abutting an endwall, the other end of the piston being axially movable in its bearing,a cylinder journalled in the cylinder bearings and telescoped over thepiston, the inner surface of the cylinder being tangential to the pistonand with it defining a pump chamber, a vane rigid with the pistonslidably engaging the cylinder and dividing the pump chamber, inlet andoutlet means communicating with the pump chamber, one through the hollowpiston, and the other interconnecting the pump chamber and the conduitopening, and replaceable shim means interposed between the removable endwall and the casing whereby minimum clearance may be maintained betweenan end of the cylinder and the corresponding end wall.

'7. In a rotary pump, a casing having an outlet and parallel end walls,at least one of the end v alls being removable from the casing, cylinderbearings in the casing intermediate the end walls, alined pistonbearings in the end walls said piston bearings having an axis spacedfrom and parallel to the axis of the cylinder bearings, a hollowcylindrical piston journalled in the piston bearings, one end of thepiston being reduced in dimeter to form a shoulder abutting an end wall,the other end of the piston being longitudinally movable in its bearing,a cylinder journalled in the cylinder bearings and telescoped over thepiston, the inner surface of the cylinder being tangential to the pistonand with it defining a pump chamber, one end of the chamber beingsubstantially sealed by an end wall, a vane rigid with the pistonslidably engaging the cylinder and longitudinally coextensive therewith,said vane dividing the pump chamber into intake and dischargecompartments, inlet means communicating with the intake compartmentthrough the hollow piston and a port in the cylinder interconnecting thedischarge compartment and the outlet, and a shim for spacing theremovable end wall from the casing thereby substantially sealing theends of the pump chamber.

8. In a rotary pump, a casing having an outlet and end walls, at leastone of the end walls being removable, cylinder bearings within thecasing, alined piston hearings in the end walls said piston bearingshaving an axis parallel to and spaced from the axis of the cylinderbearings, a hollow piston journalled in the piston bearings and reducedat one end to form a shoulder abutting an end wall, the other end of thepiston being axially movable in its bearings, cylinders telescoped overthe piston and Journalled in the cylinder bearings, each cylinder havingits inner surface tangential to the piston and with it, defining a pumpchamber, an annular ring attached to the piston abutting adjacent endsof the cylinders, vanes extending outwardly from the piston equaldistances in opposite directions and angularly disposed through 180 withrespect to each other, each vane being longitudinally coextensive withacylinder and having sliding engagement therewith, means for securingeach vane to the ring to retain the vanes in fixed relation to thepiston, inlet means communicating with the pump chambers through thepiston, each cylinder having a port interconnecting each pump chamberwith the outlet, and means for retaining the end walls of the casing ina running sealed relation to the opposite ends of the cylinders.

9. In a rotary pump, a casing having a conduit opening and parallel endwalls, cylinder bearings within the casing intermediate the end walls,axially alined piston bearings in the end walls, the major axis of thepiston bearings being spaced from, and parallel to the axis of thecylinder bearings, a hollow cylindrical piston Journalled in the pistonbearings, a cylinder intermediate the end walls telescoped over thepiston and journalled at its periphery in the cylinder bearings, thecylinder having an internal surface of revolution tangential to thepiston defining with it a pump chamber, inlet means communicating withthe pump chamber and including the hollow portion of the piston, andoutlet means communicating with the pump chamber and including theconduit opening in the casing, said cylinder being in rotatable andsealed relationship to the end walls, and a radial vane rigid with thepiston extending outwardly therefrom, and having sliding and rockingengagement with the cylinder, the vane dividing the pumping chamber intocompartments, said vane also extending inwardly into the hollow portionof the piston whereby rotary motion is imparted to the entering waterwithin the piston.

10. In a rotary pump having a hollow rotatable cylinder, a rotatablepiston mounted in tangential relation with the inner surface of thecylinder defining therewith a pump chamber, driving means rigid with thepiston slidably engaging the cylinder and dividing the pump chamber, andmeans for driving the piston, the combination therewith of a casingtelescoped over the cylinder and having end walls substantially sealingthe ends of the pumping chamber, piston bearings in the end walls, aninlet in an end wall and outlet means in the side wall of the casing,the inlet and the outlet communicating with the pump chamber on oppositesides of the dividing means, and internal bearing surfaces on the casingrotatably supporting the cylinder at its periphery.

11. For use in a rotary pump of the type described, a hollow cylindricalpiston having an external shoulder adjacent one end, an annular ringfixed on the piston intermediate the shoulder and the other end of thepiston, longitudinal vanes extending outwardly from the piston onopposite sides of and abutting the ring and angularly displaced throughwith respect to each other, a slot through a longitudinal wall of thepiston adjacent one side of each vane, and means rigid with the ringengaging the vanes for retaining the varies in fixed relation to thepiston.

12. For use ina rotary pump of the type rescri-bed, a hollow cylindricalpiston having an external shoulder adjacent one end, a ri-ngfixed on thesurface .piston intermediate the shoulder and the other end of thepiston, planar vanes extending outwardly from the piston on oppositesides of and abutting the ring and angularly displaced through 180 withrespect to each other, a transverse slot through a longitudinal wall ofthe piston adjacent one side of each vane, one of the vanes extendinginwardly into abutment with an internal wall of the piston, meansrigidly interconnecting the abutting edge of said one vane and thepiston, and means rigidly connecting both vanes to the annular ringwhereby said vanes, are retained in fixed relation to the piston.

' 13. For use in a rotary pump of the type de- Patent no. 2,516,516.

WILLIAM WARD DAVIDSON scribed, a hollow cyindrical piston having anexternal shoulder adjacent one end, a ring telescoped over the pistonand attached thereto intermediate the shoulder and the other end of thepiston, longitudinal vanes each extending outwardly from the piston onopposite sides of and abutting the ring and angularly displaced through180 with respect to each other, a transverse siot through a longitudinalwall of the piston adjacent one side of each vane, one ofthe vanesextending inwardly into abutment with an internal wall of the piston,said one vane having a transverse opening bisected by the axis of thepiston, dowels rigidly interconnecting the abutting edge of said onevane and piston, and'means rigidly interconnecting both vanes to the aular ring whereby said vanes are retained in fixed relation to thepiston.

,WILLIAM WARD DAVIDSON.

CERTIFICATE OF CORRECTION.

April 15, 1915.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 6,secand column, line 114., for disposed reed. --displaeed-; page 7, firstcolumn, lirie 14-5, for "rescribed' read "described"; same page,secondcolmnn,

line 1, for "cyindricdl" read "cylindrical"; and that the said. LettersPatent should be read with this correction therein that the same mayconfem to'the recorder the casein the Patent Office.

I Signed and sealed this n: day of June, A. n. .19 6.

(Seal) Henry Van Arsdale Acting Cominissioner of Patents.

